The influence of microbial contamination on rice bran rancidity

Abstract

Abstract The storage and utilization of rice bran are severely impeded due to the rapid rancidity caused by its lipase. However, little research was carried out to explore other factors for rice bran rancidity. In this study, five Bacilli with lipid hydrolysis abilities were isolated from rice bran and then inoculated into sample to explore the influence of microbial contamination on rancidity. Fresh rice bran was divided into four groups, including control group (CG), ultraviolet group (UG), ultraviolet-uninoculated group (UUG) and ultraviolet-five Bacilli inoculated group (UIG). The final microbial amount in UIG was significantly higher than other three groups after 31 days. The rancidity of UG was restrained to 75% compared with CG during storage. And the rancidity of UIG group was accelerated significantly after being inoculated with the five isolated strains. The increase ratio of acid values between CG, UG, UUG and UIG was about 8:6:9:15. The lipase activities performed no significant difference between CG and UG, but UIG and UUG only maintained about 40.0% and 80.0% of lipase activities. In summary, microbial contamination had a non-negligible influence on rice bran rancidity, and controlling the microbial contamination should be fully considered during the processing and preservation of rice bran.